WO2014111833A1 - Composite nanoparticle, process for manufacturing same and use thereof - Google Patents

Composite nanoparticle, process for manufacturing same and use thereof Download PDF

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WO2014111833A1
WO2014111833A1 PCT/IB2014/058170 IB2014058170W WO2014111833A1 WO 2014111833 A1 WO2014111833 A1 WO 2014111833A1 IB 2014058170 W IB2014058170 W IB 2014058170W WO 2014111833 A1 WO2014111833 A1 WO 2014111833A1
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resin
nanoparticles
composite
boron nitride
composite nanoparticles
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PCT/IB2014/058170
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French (fr)
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Jonathan SKRZYPSKI
Aurélien AUGER
Olivier Poncelet
Chloé SCHUBERT
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Commissariat A L'energie Atomique Et Aux Energies Alternatives
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Priority to EP14701436.9A priority Critical patent/EP2945906A1/en
Publication of WO2014111833A1 publication Critical patent/WO2014111833A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00—Nitrogen; Compounds thereof
    • C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
    • C01B21/064—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with boron
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/04—Compounds of zinc
    • C09C1/043—Zinc oxide
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    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/28—Compounds of silicon
    • C09C1/30—Silicic acid
    • C09C1/3045—Treatment with inorganic compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/36—Compounds of titanium
    • C09C1/3607—Titanium dioxide
    • C09C1/3653—Treatment with inorganic compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/40—Compounds of aluminium
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/62—Metallic pigments or fillers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/62—Metallic pigments or fillers
    • C09C1/627—Copper
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/06—Treatment with inorganic compounds
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
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    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
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    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
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    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/84—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by UV- or VIS- data
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    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases

Definitions

  • the invention relates to composite nanoparticles, to their method of manufacture and to their use.
  • Concentrating solar power plants come from a recent technology that has great potential for development.
  • solar radiation is concentrated via mirrors on a tube containing a heat transfer fluid that exchanges heat via a traditional Rankine cycle.
  • Water, in a secondary circuit, is transformed into steam that will drive a turbine thus producing electricity.
  • the heat transfer fluid may be water, molten salts or aromatic oils.
  • the water has a thermal conductivity of 0.6 W / m.K.
  • the aromatic oils used for solar thermal have a low conductivity (of the order of 0.130 W / m.K),
  • aromatic oils are in particular terphenyl-based oils.
  • solid boron nitride has good thermal conductivity, with values of between 20 and 140 W / m.K.
  • This material is very resistant to oxidizing atmospheres, including oxygen heating and acid attacks.
  • US Patent Application 201 1/0045223 A1 discloses a method for obtaining exfoliated hexagonal boron nitride, i.e. in the form of nanosheets.
  • This exfoliated boron nitride has mechanical, thermal and electrical properties which are superior to those of macroscopic hexagonal boron nitride. It is also a very good electrical insulator.
  • Turbostratic boron nitride is a precursor of hexagonal boron nitride but of nanometric size. It has the same type of characteristics and physical properties as exfoliated hexagonal boron nitride. Jaime Taha-Tijerina et al. in "Electrically Insulating Thermal Nano-Oils Using 2D Fillers", ACS nano, vol. 6 (2), 2012, pages 1214-1220, have demonstrated that the addition, in a mineral oil (of the nytrolOXN type), of 0.1% by weight of exfoliated hexagonal boron nitride makes it possible to increase the thermal conductivity 80% oil.
  • a mineral oil of the nytrolOXN type
  • exfoliated boron nitride is not stable in aromatic oils.
  • the invention aims to overcome the disadvantages of the prior art by providing composite nanoparticles comprising stable boron nitride in aromatic oils in particular, in any case having a high affinity for organic matrices, and having good thermal conductivity, which are synthesized with almost quantitative yield.
  • the invention proposes composite nanoparticles made of a material chosen from Ti0 2 , Zr0 2 , ZnO, SiO 2 , ⁇ 1 2 ⁇ 3 3 Pt, Au, Ag, and Cu and a peripheral outer part made of turbostratic boron nitride ( t-BN).
  • Composite nanoparticles are made of a heart and a shell.
  • the central inner part, called the core, of these composite nanoparticles has dimensions preferably less than 100 nm, typically a diameter of between 10 and 100 nm and a globally spheroidal shape, in said material, and their peripheral outer part, or shell, turbostratic boron nitride completely covers the nanoparticle with a thickness of between 1 and 10 nm, preferably a thickness of 5 nm.
  • the tBN shell is preferably dense,
  • said central internal portion is Ti0 2 or A1 2 0 3 .
  • said central internal portion is Ti0 2 .
  • the invention also proposes the use of the composite nanoparticles of the invention as a filler for increasing the thermal conductivity of the materials in which it is integrated.
  • the material in which the composite nanoparticles are integrated is a resin chosen from an epoxy resin, a polyimide resin and a polyurethane resin, preferably an epoxy resin.
  • the composite nanoparticles represent between 0.1 and 5% (by weight), relative to the total weight of the non-crosslinked resin plus the composite nanoparticles.
  • this mass percentage is between 0.5 and 2%.
  • the invention also proposes a composite material comprising a resin in which composite nanoparticles according to the invention are embedded.
  • This resin is, in particular, chosen from an epoxy resin, a polyimide resin and a polyurethane resin, preferably an epoxy resin.
  • the invention also proposes the use of the nanoparticles according to the invention as an agent for protecting against UV rays.
  • the invention also proposes the use of the nanoparticles according to the invention as an opacifying agent for papermaking fibers.
  • the invention finally proposes a process for synthesizing composite nanoparticles according to the invention, characterized in that it comprises the following steps:
  • step b) drying the solid obtained after step b) for between 24 and 120 hours, preferably 96 hours, at a temperature between 60 and 100 ° C, preferably at 80 ° C, and
  • step d) heat treatment of the solid obtained in step c) at a temperature between 400 and 500 ° C, preferably at 500 ° C, for between 1 and 5 hours, preferably 3 hours.
  • the amount of urea is twice the stoichiometric amount of boron provided by boric acid.
  • FIG. 1 represents the X-ray diffractogram obtained on turbostratic boron nitride synthesized from boric acid and urea,
  • FIG. 2 represents a photograph taken under the transmission electron microscope of nanoparticles according to the invention consisting of a central internal part made of Ti0 2 covered with a peripheral outer layer of turbostratic boron nitride,
  • FIG. 3 represents the Raman spectrum of Ti0 2 between 200 and
  • FIG. 4 represents the Raman spectrum of the sample of turbostratic boron nitride synthesized in the comparative example
  • FIG. 5 represents the Raman spectrum of the nanoparticles according to the invention synthesized in Example 1,
  • FIG. 6 is a diagram showing the thermal diffusivity, at 23 ° C., of an epoxy resin sample, synthesized according to comparative example 1, and of an epoxy resin sample containing composite nanoparticles according to the invention constituted a central Ti0 2 internal part and a turbostratic boron nitride peripheral outer part, synthesized in Example 1,
  • FIG. 7 shows the results of the breakdown test of the epoxy resin used in example 2.
  • FIG. 8 shows the results of the breakdown test carried out on the epoxy resin used in example 2, loaded with 1% by weight, relative to the total resin mass plus filler, of composite nanoparticles according to the invention consisting of a central internal part made of Ti0 2 and a peripheral outer part made of turbostratic boron nitride, synthesized in Example 1.
  • the invention is based on the discovery that the turbostratic boron nitride when deposited on nanoparticles Ti0 2, Zr0 2, ZnO, Si0 2j of A1 2 0 3 and of metals such as Pt, Au, Ag, Cu, gives rise to composite nanoparticles with high affinity for organic matrices and good thermal conductivity.
  • These nanoparticles thus consist of an internal central part made of Ti0 2 , Zr0 2 , ZnO, Si0 2 , Al 2 O 3 and metals such as Pt, Au, Ag, Cu, and an external part. peripheral in t-BN.
  • the invention is also based on the surprising discovery that the "shell" (external peripheral part) of turbostratic boron nitride is impossible to attack chemically, although its growth has taken place at low temperature, which makes it possible to obtain size charges. nanoscale used in organic materials, or water, especially epoxy resins, to increase the thermal conductivity without affecting the breakdown properties of the material obtained.
  • the nanoparticles of the invention may also be used in other applications depending on the composition of the central inner portion (or heart).
  • the central inner part of the nanoparticles is composed of titanium oxide (T1O2), which has a UV protection effect without photocatalytic activity or which is widely used as an opacifying agent in the paper industry, but with the surface of the TiO 2 particles chemically treated so as to inhibit its photocatalytic properties which end up degrading the organic environment of the particles
  • the composite nanoparticles according to the invention consisting of a central internal part (core) Ti0 2 and a outer peripheral part (shell) completely covering this inner inner part, can be easily dispersed in any organic solvent. They can thus be integrated very easily in cosmetic creams or be used as such as opacifying agent in the paper industry.
  • the composite nanoparticles of the invention can be used both for the electrical and conductivity properties of turbostratic boron nitride and for the properties of the core that they contain.
  • the composite nanoparticles of the invention are therefore formed of a central internal part made of a material chosen from Ti0 2 , Zr0 2 , ZnO, SiO 2 , Al 2 O 3, Pt, Au, Ag, Cu, etc., completely covered with a turbostratic boron nitride layer.
  • the central inner part consists of nanoparticles having a spherical shape with a diameter of between 10 and 100 nm, preferably with a diameter of 20 nm, which are entirely covered with a layer of turbostratic boron nitride having a thickness of between 1 and 10 nm, preferably with a layer of 5 nm turbostratic boron nitride. thickness.
  • the invention also proposes a process for synthesizing these composite nanoparticles which makes it possible to obtain a good yield.
  • This process comprises dispersing the desired nanoparticles to form the central inner part of the composite nanoparticles using an ultrasound probe in an alcoholic solvent such as ethanol in which boric acid and boric acid have been previously dissolved.
  • alcoholic solvent such as ethanol in which boric acid and boric acid have been previously dissolved.
  • urea which are precursors of turbostratic boron nitride.
  • the duration of the dispersion varies between 15 minutes and 4 hours. Preferably, it is 1 hour.
  • the solvent is evaporated by any means known to those skilled in the art.
  • the solid thus obtained is then dried for between 24 hours and 120 hours, preferably for 4 days at a temperature between 60 and 100 ° C, preferably at a temperature of 80 ° C.
  • the obtained powder is annealed, that is to say undergoes heat treatment at a temperature between 400 ° C and 500 ° C, preferably at a temperature of 500 ° C, for 1 and 5 hours, preferably during 3 hours.
  • the temperature of this annealing should not be higher than 500 ° C as this could result in sintering of the composite nanoparticles, and therefore, an increase in their sizes.
  • TiO 2 nanoparticles having a substantially spherical shape and a diameter of about 20 nm are dispersed, using an ultrasound probe, in 80 ml of ethanol in which 1.09 g of boric acid and 2.98 g of urea were previously dissolved.
  • a volume of 40 mL of distilled water is added at once, before sonication.
  • the amount of urea used during this dispersing step corresponds to twice the stoichiometric amount of boron provided by boric acid.
  • the ultrasound treatment lasts 1 hour.
  • the powder then obtained is then annealed for a period of 3 hours at 500 ° C. in an oven.
  • the boron nitride will serve as a reference to compare with the composite nanoparticles of the invention, for the analyzes,
  • This turbostratic boron nitride was prepared using 3.8 g of boric acid and 7.4 g of urea dissolved in 200 ml of ethanol following the same protocol as in Example 1, with the exception the presence of TiO 2 nanoparticles.
  • Figure 1 shows the X-ray diffraction pattern of the t-BN sample made in Comparative Example 1.
  • FIG. 2 shows a transmission electron microscope image of the composite nanoparticles obtained in Example 1.
  • FIG. 2 there is indeed a shell, or gangue, or external peripheral portion, having a thickness of approximately 5 nm, which surrounds the TiO 2 nanoparticles.
  • turbostratic boron at the periphery of the TiO 2 nanoparticles was confirmed using Raman spectroscopy
  • FIG. 3 shows the Raman spectrum of the Ti ⁇ nanoparticles used in Example 1.
  • This Raman spectrum has three peaks at 395 cm -1 , 516 cm -1 and 637 cm -1 .
  • Figure 4 shows the Raman spectrum of the t-BN sample synthesized in Comparative Example 1. This Raman spectrum has a peak at 881 cm -1 .
  • Figure 5 shows the Raman spectrum of the composite nanoparticles synthesized in Example 1.
  • the peaks at 395 cm -1 , 516 cm -1 and 637 cm -1 representative of Ti (1 ⁇ 2 are present as well as the peak at 881 cm -1 representative of turbostratic boron nitride.
  • the composite nanoparticles in Example 1 consist of TiO 2 nanoparticles coated with turbostratic boron nitride.
  • This example is intended to show the effectiveness of the sealing of the outer peripheral part or shell or gangue composite nanoparticles manufactured in Example 1.
  • Example 1 the nanoparticles of Example 1 were embedded in a non-polymerized resin.
  • the amount of composite nanoparticles of Example 1 was 1% by weight relative to the total mass of unpolymerized resin plus composite nanoparticles of Example 1.
  • the resin was an epoxy resin.
  • the Ti0 2 can not be used as a filler for applications in resins to increase the thermal conductivity of these resins without affecting the breakdown properties: in the field the ions of the surface of TiO 2 particles (Ti 4 + or Ti 3 + ) or even the oxygen radicals move and eventually snap the sample.
  • FIG. 7 represents the results of the breakdown test of the sample obtained in Comparative Example 2: the breakdown voltage is 20 kV / mm.
  • FIG. 8 represents the results of the breakdown test performed on the sample obtained in example 2. This figure shows that in this case, the breakdown voltage is 35 kV / mm.
  • Example 1 The TiO 2 nanoparticles used in Example 1 were dispersed in the same epoxy resin as in Example 2 and in Comparative Example 2. However, the plate obtained was not homogeneous and no diffusivity and breakdown test was carried out because the result obtained would have been different depending on the plate chosen to carry out a measurement. This shows that there is no compatibility between TiO 2 nanoparticles and organic resins.
  • the turbostratic boron nitride obtained in Comparative Example 1 was introduced into the same epoxy resin as used in Example 2 and Comparative Example 2.
  • turbostratic boron nitride The amount of turbostratic boron nitride was 1% by weight, based on the total mass of unpolymerized resin plus turbostratic boron nitride.
  • FIG. 6 shows the thermal diffusivity values at 23 ° C. of the samples obtained in Comparative Example 2, Comparative Example 3 and Example 2.
  • the thermal conductivity of the sample obtained in example 2, containing the composite nanoparticles of the invention is increased by 16% relative to the thermal conductivity of the sample obtained in FIG. Comparative Example 2, consisting solely of epoxy resin and with respect to the sample obtained in Example 3 containing only turbostratic boron nitride.
  • the composite nanoparticles of the invention can be used as a filler to increase the thermal conductivity of resins or aromatic fluids such as terphenyl-based oils.

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Abstract

The invention relates to composite nanoparticles, to the process for producing same and to the use thereof. The composite nanoparticles of the invention comprise a central part made of a material chosen from TiO2, ZrO2, ZnO, SiO2, Al2O3, Pt, Au, Ag and Cu, and a peripheral external part made of turbostratic boron nitride (t-BN). The invention is of use in the field of heat-exchange fluids, in particular.

Description

NANOPARTICULE COMPOSITE, SON PROCEDE DE FABRICATION ET SON UTILISATION  COMPOSITE NANOPARTICLE, PROCESS FOR PRODUCING THE SAME, AND USE THEREOF
L'invention se rapporte à des nanoparticuies composites, à leur procédé de fabrication et à leur utilisation. The invention relates to composite nanoparticles, to their method of manufacture and to their use.
Les centrales solaires à concentration sont issues d'une technologie récente qui possède un grand potentiel en termes de développement. Dans ces centrales, la radiation solaire est concentrée via des miroirs sur un tube contenant un fluide caloporteur qui échange la chaleur via un cycle de Rankine traditionnel. De l'eau, dans un circuit secondaire, est transformée en vapeur qui va entraîner une turbine produisant ainsi de l'électricité.  Concentrating solar power plants come from a recent technology that has great potential for development. In these plants, solar radiation is concentrated via mirrors on a tube containing a heat transfer fluid that exchanges heat via a traditional Rankine cycle. Water, in a secondary circuit, is transformed into steam that will drive a turbine thus producing electricity.
Le fluide caloporteur peut être de l'eau, des sels fondus ou bien des huiles aromatiques.  The heat transfer fluid may be water, molten salts or aromatic oils.
L'eau présente une conductivité thermique de 0,6 W/m.K.  The water has a thermal conductivity of 0.6 W / m.K.
Les huiles aromatiques utilisées pour le solaire thermique présentent une faible conductivité (de l'ordre de 0,130 W/m.K),  The aromatic oils used for solar thermal have a low conductivity (of the order of 0.130 W / m.K),
Ces huiles aromatiques sont en particulier des huiles à base de terphényle.  These aromatic oils are in particular terphenyl-based oils.
Il existe un besoin pour des nanoparticuies permettant d'augmenter la conductivité thermique du fluide caloporteur (les huiles aromatiques, les sels fondus ou l'eau) lorsqu' intégrées dans ce fluide caloporteur.  There is a need for nanoparticles to increase the thermal conductivity of the heat transfer fluid (aromatic oils, molten salts or water) when integrated in the heat transfer fluid.
Par ailleurs, il est connu que le nitrure de bore massif présente une bonne conductivité thermique, avec des valeurs comprises entre 20 et 140 W/m.K.  Furthermore, it is known that solid boron nitride has good thermal conductivity, with values of between 20 and 140 W / m.K.
Ce matériau est très résistant aux atmosphères oxydantes, et notamment au chauffage sous oxygène et aux attaques acides.  This material is very resistant to oxidizing atmospheres, including oxygen heating and acid attacks.
La demande de brevet US 201 1/0045223 Al décrit un procédé pour obtenir du nitrure de bore hexagonal exfolié, c'est-à-dire sous forme de nanofeuillets.  US Patent Application 201 1/0045223 A1 discloses a method for obtaining exfoliated hexagonal boron nitride, i.e. in the form of nanosheets.
Ce nitrure de bore exfolié présente des propriétés mécaniques, thermiques et électriques qui sont supérieures à celles du nitrure de bore hexagonal macroscopique. C'est aussi un très bon isolant électrique.  This exfoliated boron nitride has mechanical, thermal and electrical properties which are superior to those of macroscopic hexagonal boron nitride. It is also a very good electrical insulator.
Le nitrure de bore turbostratique (t-BN) est un précurseur du nitrure de bore hexagonal mais de taille nanométrique. Il présente le même type de caractéristiques et de propriétés physiques que le nitrure de bore hexagonal exfolié. Jaime Taha-Tijerina et al. dans " Electrically Insulating Thermal Nano-Oils Using 2D Fillers", ACS nano, vol. 6 (2), 2012, pages 1214-1220, ont mis en évidence que l'ajout, dans une huile minérale (du type nytrolOXN), de 0,1% massique de nitrure de bore hexagonal exfolié permet d'augmenter la conductivité thermique de l'huile de 80 %. Turbostratic boron nitride (t-BN) is a precursor of hexagonal boron nitride but of nanometric size. It has the same type of characteristics and physical properties as exfoliated hexagonal boron nitride. Jaime Taha-Tijerina et al. in "Electrically Insulating Thermal Nano-Oils Using 2D Fillers", ACS nano, vol. 6 (2), 2012, pages 1214-1220, have demonstrated that the addition, in a mineral oil (of the nytrolOXN type), of 0.1% by weight of exfoliated hexagonal boron nitride makes it possible to increase the thermal conductivity 80% oil.
Cependant, le nitrure de bore exfolié n'est pas stable dans les huiles aromatiques.  However, exfoliated boron nitride is not stable in aromatic oils.
De plus, la méthode décrite de synthèse des nitrures de bore hexagonal exfolié ne permet pas d'obtenir de très grandes quantités de matière, les rendements de cette synthèse étant très faibles, c'est-à-dire de l'ordre de 0,1%.  In addition, the described method of synthesis of exfoliated hexagonal boron nitrides does not make it possible to obtain very large quantities of material, the yields of this synthesis being very low, ie of the order of 0, 1%.
L'invention vise à pallier les inconvénients de l'art antérieur en proposant des nanoparticules composites comprenant du nitrure de bore stable dans les huiles aromatiques en particulier, en tout cas ayant une grande affinité pour les matrices organiques, et ayant une bonne conductivité thermique, qui sont synthétisées avec un rendement quasi quantitatif.  The invention aims to overcome the disadvantages of the prior art by providing composite nanoparticles comprising stable boron nitride in aromatic oils in particular, in any case having a high affinity for organic matrices, and having good thermal conductivity, which are synthesized with almost quantitative yield.
A cet effet, l'invention propose des nanoparticules composites en un matériau choisi parmi Ti02, Zr02, ZnO, Si02, Α12θ33 Pt, Au, Ag, et Cu et une partie externe périphérique en nitrure de bore turbostratique (t-BN). For this purpose, the invention proposes composite nanoparticles made of a material chosen from Ti0 2 , Zr0 2 , ZnO, SiO 2 , Α 1 2 θ 3 3 Pt, Au, Ag, and Cu and a peripheral outer part made of turbostratic boron nitride ( t-BN).
Les nanoparticules composites sont donc faites d'un cœur et d'une coquille.  Composite nanoparticles are made of a heart and a shell.
La partie interne centrale, dite cœur, de ces nanoparticules composites a des dimensions de préférence inférieure à 100 nm, typiquement un diamètre compris entre 10 et 100 nm et une forme globalement sphéroïdale, en ledit matériau, et leur partie externe périphérique, ou coquille, en nitrure de bore turbostratique couvre entièrement la nanoparticule avec une épaisseur comprise entre 1 et 10 nm, de préférence une épaisseur de 5 nm.  The central inner part, called the core, of these composite nanoparticles has dimensions preferably less than 100 nm, typically a diameter of between 10 and 100 nm and a globally spheroidal shape, in said material, and their peripheral outer part, or shell, turbostratic boron nitride completely covers the nanoparticle with a thickness of between 1 and 10 nm, preferably a thickness of 5 nm.
La coquille en tBN est de préférence dense,  The tBN shell is preferably dense,
De préférence, ladite partie interne centrale est en Ti02 ou en A1203. Preferably, said central internal portion is Ti0 2 or A1 2 0 3 .
Plus préférablement, ladite partie interne centrale est en Ti02. More preferably, said central internal portion is Ti0 2 .
L'invention propose aussi l'utilisation des nanoparticules composites de l'invention en tant que charge pour augmenter la conductivité thermique des matériaux dans lesquels elle est intégrée. En particulier, le matériau dans lequel les nanoparticules composites sont intégrées est une résine choisie parmi une résine époxy, une résine polyimide et une résine polyuréthane, de préférence est une résine époxy. The invention also proposes the use of the composite nanoparticles of the invention as a filler for increasing the thermal conductivity of the materials in which it is integrated. In particular, the material in which the composite nanoparticles are integrated is a resin chosen from an epoxy resin, a polyimide resin and a polyurethane resin, preferably an epoxy resin.
De préférence, les nanoparticules composites représentent entre 0,1 et 5% (massique), par rapport au poids total de la résine non réticulée plus les nanoparticules composites.  Preferably, the composite nanoparticles represent between 0.1 and 5% (by weight), relative to the total weight of the non-crosslinked resin plus the composite nanoparticles.
De préférence, ce pourcentage massique est compris entre 0,5 et 2%. Preferably, this mass percentage is between 0.5 and 2%.
L'invention propose également un matériau composite comprenant une résine dans laquelle des nanoparticules composites selon l'invention sont noyées. The invention also proposes a composite material comprising a resin in which composite nanoparticles according to the invention are embedded.
Cette résine est, en particulier, choisie parmi une résine époxy, une résine polyimide et une résine polyuréthane, de préférence est une résine époxy.  This resin is, in particular, chosen from an epoxy resin, a polyimide resin and a polyurethane resin, preferably an epoxy resin.
L'invention propose aussi l'utilisation des nanoparticules selon l'invention en tant qu'agent de protection contre les rayons UV.  The invention also proposes the use of the nanoparticles according to the invention as an agent for protecting against UV rays.
L'invention propose encore l'utilisation des nanoparticules selon l'invention en tant qu'agent opacifiant pour des fibres papetières.  The invention also proposes the use of the nanoparticles according to the invention as an opacifying agent for papermaking fibers.
L'invention propose enfin un procédé de synthèse de nanoparticules composites selon l'invention, caractérisé en ce qu'il comprend les étapes suivantes :  The invention finally proposes a process for synthesizing composite nanoparticles according to the invention, characterized in that it comprises the following steps:
a) dispersion de nanoparticules en un matériau choisi parmi Ti02, Zr02, ZnO, Si02, AI2O3, Pt, Au, Ag, et Cu, dans de réthanol dans lequel de l'acide borique et de l'urée ont été dissous, par traitement aux ultrasons pendant entre 15 minutes et 4 heures, après ajout d'eau, a) dispersion of nanoparticles into a material selected from Ti0 2 , Zr0 2 , ZnO, SiO 2 , Al 2 O 3, Pt, Au, Ag, and Cu, in ethanol in which boric acid and urea have dissolved, by ultrasonic treatment for between 15 minutes and 4 hours, after addition of water,
b) évaporatïon de l'éthanol,  b) evaporation of ethanol,
c) séchage du solide obtenu après l'étape b) pendant entre 24 et 120 heures, de préférence 96 heures, à une température comprise entre 60 et 100°C, de préférence à 80°C, et  c) drying the solid obtained after step b) for between 24 and 120 hours, preferably 96 hours, at a temperature between 60 and 100 ° C, preferably at 80 ° C, and
d) traitement thermique du solide obtenu à l'étape c) à une température comprise entre 400 et 500°C, de préférence à 500°C, pendant entre 1 et 5 heures, de préférence 3 heures.  d) heat treatment of the solid obtained in step c) at a temperature between 400 and 500 ° C, preferably at 500 ° C, for between 1 and 5 hours, preferably 3 hours.
De préférence, à l'étape a), la quantité d'urée correspond à deux fois la quantité stœchiométrique de bore apportée par l'acide borique. L'invention sera mieux comprise et d'autres caractéristiques et avantages de celle-ci apparaîtront plus clairement à la lecture de la description explicative qui suit et qui est faite en référence aux figures dans lesquelles : Preferably, in step a), the amount of urea is twice the stoichiometric amount of boron provided by boric acid. The invention will be better understood and other characteristics and advantages thereof will appear more clearly on reading the explanatory description which follows and which is made with reference to the figures in which:
- la figure 1 représente le diffractogramme des rayons X obtenu sur du nitrure de bore turbostratique synthétisé à partir d'acide borique et d'urée,  FIG. 1 represents the X-ray diffractogram obtained on turbostratic boron nitride synthesized from boric acid and urea,
- la figure 2 représente une photographie prise au microscope électronique à transmission de nanoparticules selon l'invention constituées d'une partie interne centrale en Ti02 recouverte d'une couche externe périphérique de nitrure de bore turbostratique, FIG. 2 represents a photograph taken under the transmission electron microscope of nanoparticles according to the invention consisting of a central internal part made of Ti0 2 covered with a peripheral outer layer of turbostratic boron nitride,
- la figure 3 représente le spectre Raman de Ti02 entre 200 etFIG. 3 represents the Raman spectrum of Ti0 2 between 200 and
900 cm-1, 900 cm -1 ,
- la figure 4 représente le spectre Raman de l'échantillon de nitrure de bore turbostratique synthétisé à l'exemple comparatif,  FIG. 4 represents the Raman spectrum of the sample of turbostratic boron nitride synthesized in the comparative example,
- la figure 5 représente le spectre Raman des nanoparticules selon l 'invention synthétisées à 1 ' exemple 1 ,  FIG. 5 represents the Raman spectrum of the nanoparticles according to the invention synthesized in Example 1,
- la figure 6 est un diagramme montrant la diffusivité thermique, à 23°C, d'un échantillon de résine époxy, synthétisé selon l'exemple comparatif 1, et d'un échantillon de résine époxy contenant des nanoparticules composites selon l'invention constituées d'une partie interne centrale en Ti02 et d'une, partie externe périphérique en nitrure de bore turbostratique, synthétisées à l'exemple 1, FIG. 6 is a diagram showing the thermal diffusivity, at 23 ° C., of an epoxy resin sample, synthesized according to comparative example 1, and of an epoxy resin sample containing composite nanoparticles according to the invention constituted a central Ti0 2 internal part and a turbostratic boron nitride peripheral outer part, synthesized in Example 1,
- la figure 7 montre les résultats du test de claquage de la résine époxy utilisée à l'exemple 2, et  FIG. 7 shows the results of the breakdown test of the epoxy resin used in example 2, and
- la figure 8 montre les résultats du test de claquage effectué sur la résine époxy utilisée à l'exemple 2, chargée avec 1 % en masse, par rapport à la masse totale résine plus charge, de nanoparticules composites selon l'invention constituées d'une partie interne centrale en Ti02 et d'une partie externe périphérique en nitrure de bore turbostratique, synthétisé à l'exemple 1. FIG. 8 shows the results of the breakdown test carried out on the epoxy resin used in example 2, loaded with 1% by weight, relative to the total resin mass plus filler, of composite nanoparticles according to the invention consisting of a central internal part made of Ti0 2 and a peripheral outer part made of turbostratic boron nitride, synthesized in Example 1.
L'invention repose sur la découverte que le nitrure de bore turbostratique lorsque déposé sur des nanoparticules de Ti02, de Zr02, de ZnO, de Si02j de A1203 et de métaux tels que Pt, Au, Ag, Cu, donne naissance à des nanoparticules composites ayant une grande affinité pour les matrices organiques et une bonne conductivité thermique. Ces nanoparticules sont ainsi constituées d'une partie centrale interne en Ti02, en Zr02, en ZnO, en Si02, en A1203 et en métaux tels que Pt, Au, Ag, Cu, et d'une partie externe périphérique en t-BN. The invention is based on the discovery that the turbostratic boron nitride when deposited on nanoparticles Ti0 2, Zr0 2, ZnO, Si0 2j of A1 2 0 3 and of metals such as Pt, Au, Ag, Cu, gives rise to composite nanoparticles with high affinity for organic matrices and good thermal conductivity. These nanoparticles thus consist of an internal central part made of Ti0 2 , Zr0 2 , ZnO, Si0 2 , Al 2 O 3 and metals such as Pt, Au, Ag, Cu, and an external part. peripheral in t-BN.
L'invention repose également sur la découverte surprenante que la "coquille" (partie externe périphérique) en nitrure de bore turbostratique est impossible à attaquer chimiquement bien que sa croissance ait eu lieu à basse température, ce qui permet d'obtenir des charges de tailles nanométriques utilisables dans des matériaux organiques, ou de l'eau, en particulier des résines époxy, pour en augmenter la conductivité thermique sans affecter les propriétés de claquage du matériau obtenu.  The invention is also based on the surprising discovery that the "shell" (external peripheral part) of turbostratic boron nitride is impossible to attack chemically, although its growth has taken place at low temperature, which makes it possible to obtain size charges. nanoscale used in organic materials, or water, especially epoxy resins, to increase the thermal conductivity without affecting the breakdown properties of the material obtained.
Les nanoparticules de l'invention pourront être également utilisées dans d'autres applications en fonction de la composition de la partie interne centrale (ou cœur). Par exemple, lorsque la partie interne centrale des nanoparticules est composée d'oxyde de titane (T1O2), qui a un effet de protection anti-UV sans activité photocatalytique ou qui est largement utilisé comme agent opacifiant dans l'industrie papetière, mais avec la surface des particules de Ti02 chimiquement traitées de manière à inhiber ses propriétés photocatalytiques qui finissent par dégrader l'environnement organique des particules, les nanoparticules composites selon l'invention constituées d'une partie interne centrale (cœur) en Ti02 et d'une partie externe périphérique (coquille) recouvrant entièrement cette partie interne centrale, pourront être facilement dispersées dans tout solvant organique. Elles pourront être ainsi intégrées très facilement dans des crèmes cosmétiques ou être utilisées telles quelles comme agent opacifiant dans l'industrie papetière. The nanoparticles of the invention may also be used in other applications depending on the composition of the central inner portion (or heart). For example, when the central inner part of the nanoparticles is composed of titanium oxide (T1O2), which has a UV protection effect without photocatalytic activity or which is widely used as an opacifying agent in the paper industry, but with the surface of the TiO 2 particles chemically treated so as to inhibit its photocatalytic properties which end up degrading the organic environment of the particles, the composite nanoparticles according to the invention consisting of a central internal part (core) Ti0 2 and a outer peripheral part (shell) completely covering this inner inner part, can be easily dispersed in any organic solvent. They can thus be integrated very easily in cosmetic creams or be used as such as opacifying agent in the paper industry.
Ainsi, les nanoparticules composites de l'invention pourront être utilisées aussi bien pour les propriétés électriques et de conductivité du nitrure de bore turbostratique que pour les propriétés du cœur qu'elles contiennent.  Thus, the composite nanoparticles of the invention can be used both for the electrical and conductivity properties of turbostratic boron nitride and for the properties of the core that they contain.
Les nanoparticules composites de l'invention sont donc formées d'une partie interne centrale en un matériau choisi parmi Ti02, Zr02, ZnO, Si02, AI2O3, Pt, Au, Ag, Cu, etc .. complètement recouvertes d'une couche de nitrure de bore turbostratique. The composite nanoparticles of the invention are therefore formed of a central internal part made of a material chosen from Ti0 2 , Zr0 2 , ZnO, SiO 2 , Al 2 O 3, Pt, Au, Ag, Cu, etc., completely covered with a turbostratic boron nitride layer.
De préférence, la partie interne centrale est constituée de nanoparticules ayant une forme sphérique d'un diamètre compris entre 10 et 100 nm, de préférence d'un diamètre de 20 nm, qui sont entièrement recouvertes d'une couche de nitrure de bore turbostratique d'une épaisseur comprise entre 1 et 10 nm, de préférence d'une couche de nitrure de bore turbostratique de 5 nm d'épaisseur. Preferably, the central inner part consists of nanoparticles having a spherical shape with a diameter of between 10 and 100 nm, preferably with a diameter of 20 nm, which are entirely covered with a layer of turbostratic boron nitride having a thickness of between 1 and 10 nm, preferably with a layer of 5 nm turbostratic boron nitride. thickness.
L'invention propose également un procédé de synthèse de ces nanoparticules composites qui permet d'obtenir un bon rendement.  The invention also proposes a process for synthesizing these composite nanoparticles which makes it possible to obtain a good yield.
Ce procédé comprend la dispersion des nanoparticules voulues pour former la partie interne centrale des nanoparticules composites à l'aide d'une sonde à ultrasons dans un solvant alcoolique tel que l'éthanol dans lequel ont été préalablement dissous de l'acide borique et de l'urée, qui sont des précurseurs du nitrure de bore turbostratique.  This process comprises dispersing the desired nanoparticles to form the central inner part of the composite nanoparticles using an ultrasound probe in an alcoholic solvent such as ethanol in which boric acid and boric acid have been previously dissolved. urea, which are precursors of turbostratic boron nitride.
La durée de la dispersion varie entre 15 minutes et 4 heures. De préférence, elle est de 1 heure.  The duration of the dispersion varies between 15 minutes and 4 hours. Preferably, it is 1 hour.
Pendant cette étape de dispersion, de l'eau est ajoutée pour éviter la formation d'éthanoate de bore et sa vaporisation.  During this dispersion step, water is added to prevent the formation of boron ethanoate and its vaporization.
L'eau est ajoutée dès le début, juste avant le traitement US, aucune eau n'est rajoutée par la suite.  Water is added from the beginning, just before the US treatment, no water is added thereafter.
A la fin de l'étape ci-dessus de dispersion, le solvant est évaporé par tout moyen connu de l'homme de l'art.  At the end of the above dispersing step, the solvent is evaporated by any means known to those skilled in the art.
Le solide ainsi obtenu est ensuite séché pendant entre 24 heures et 120 heures, de préférence pendant 4 jours à une température comprise entre 60 et 100°C, de préférence à une température de 80°C.  The solid thus obtained is then dried for between 24 hours and 120 hours, preferably for 4 days at a temperature between 60 and 100 ° C, preferably at a temperature of 80 ° C.
Ensuite, la poudre obtenue est recuite, c'est-à-dire subit un traitement thermique à une température comprise entre 400°C et 500°C, de préférence à une température de 500°C, pendant 1 et 5 heures, de préférence pendant 3 heures.  Then, the obtained powder is annealed, that is to say undergoes heat treatment at a temperature between 400 ° C and 500 ° C, preferably at a temperature of 500 ° C, for 1 and 5 hours, preferably during 3 hours.
La température de ce recuit ne doit pas être supérieure à 500°C car cela pourrait entraîner un frittage des nanoparticules composites, et donc, une augmentation de leurs tailles.  The temperature of this annealing should not be higher than 500 ° C as this could result in sintering of the composite nanoparticles, and therefore, an increase in their sizes.
Lors de la dispersion au cours de laquelle le nitrure de bore se forme et recouvre les nanoparticules destinées à former la partie centrale interne des nanoparticules composites de l'invention, il est préférable d'utiliser une quantité d'urée correspondant à deux fois la quantité stœchiométrique de bore apportée par l'acide borique. Afin de mieux faire comprendre l'invention, on va maintenant en donner, à titre purement illustratifs et non limitatifs, plusieurs exemples de mise en oeuvre. During the dispersion during which the boron nitride is formed and covers the nanoparticles intended to form the inner central portion of the composite nanoparticles of the invention, it is preferable to use a quantity of urea corresponding to twice the amount stoichiometric boron provided by boric acid. In order to better understand the invention, we will now give, by way of illustration and not limitation, several examples of implementation.
Exemple 1  Example 1
Synthèse de nanoparticules comprenant une partie centrale en T1O2 et une partie périphérique en nitrure de bore turbostratique. Synthesis of nanoparticles comprising a central part in T1O 2 and a peripheral part in turbostratic boron nitride.
2 g de nanoparticules de Ti02 ayant une forme sensiblement sphérique et un diamètre de 20 nm environ, sont dispersés, à l'aide d'une sonde à ultrasons, dans 80 mL d'éthanol dans lesquels 1,09 g d'acide borique et 2,98 g d'urée ont été préalablement dissous. 2 g of TiO 2 nanoparticles having a substantially spherical shape and a diameter of about 20 nm are dispersed, using an ultrasound probe, in 80 ml of ethanol in which 1.09 g of boric acid and 2.98 g of urea were previously dissolved.
Un volume de 40 mL d'eau distillée est ajouté en une fois, avant le traitement aux ultrasons.  A volume of 40 mL of distilled water is added at once, before sonication.
On notera que la quantité d'urée utilisée lors de cette étape de dispersion correspond à deux fois la quantité stœchiométrique de bore apportée par l'acide borique.  It will be noted that the amount of urea used during this dispersing step corresponds to twice the stoichiometric amount of boron provided by boric acid.
Le traitement aux ultrasons a une durée de 1 heure.  The ultrasound treatment lasts 1 hour.
Puis, le solvant éthanol a été évaporé en utilisant un évaporateur rotatif, à 80°C.  Then, the ethanol solvent was evaporated using a rotary evaporator at 80 ° C.
La poudre alors obtenue subit ensuite un recuit d'une durée de 3 heures à 500°C dans un four.  The powder then obtained is then annealed for a period of 3 hours at 500 ° C. in an oven.
Exemple comparatif 1  Comparative Example 1
Synthèse de nitrure de bore turbostratique seul.  Synthesis of turbostratic boron nitride alone.
Le nitrure de bore servira de référence à comparer aux nanoparticules composites de l'invention, pour les analyses,  The boron nitride will serve as a reference to compare with the composite nanoparticles of the invention, for the analyzes,
Ce nitrure de bore turbostratique a été préparé en utilisant 3,8 g d'acide borique et 7,4 g d'urée dissous dans 200 mL d'éthanol en suivant le même protocole qu'à l'exemple 1, à l'exception de la présence de nanoparticules de Ti02. This turbostratic boron nitride was prepared using 3.8 g of boric acid and 7.4 g of urea dissolved in 200 ml of ethanol following the same protocol as in Example 1, with the exception the presence of TiO 2 nanoparticles.
La figure 1 montre le diagramme de diffraction des rayons X de l'échantillon de t-BN fabriqué à l'exemple comparatif 1.  Figure 1 shows the X-ray diffraction pattern of the t-BN sample made in Comparative Example 1.
Ce diagramme des rayons X correspond bien au diffracto gramme présent dans la littérature (J. Thomas et al., Journal of the American Chemical Society, 84, 24, 1963, 4619) : il y a bien deux pics présents qui correspondent au nitrure de bore turbostratique, le premier pic très élargi correspondant, quant à lui, au support en silice utilisé pour immobiliser le nitrure de bore turbostratique. This X-ray diagram corresponds well to the diffractogram present in the literature (J. Thomas et al., Journal of the American Chemical Society, 84, 24, 1963, 4619): there are two peaks present which correspond to the turbostratic boron nitride, the first enlarged peak corresponding, for its part, to the silica support used to immobilize the turbostratic boron nitride.
Ainsi, la synthèse utilisée permet d'obtenir le nitrure de bore turbostratique souhaité.  Thus, the synthesis used makes it possible to obtain the desired turbostratic boron nitride.
La figure 2 montre une image prise au microscope électronique à transmission des nanoparticules composites obtenues à l'exemple 1.  FIG. 2 shows a transmission electron microscope image of the composite nanoparticles obtained in Example 1.
Comme on le voit sur la figure 2, il y a bien une coquille, ou gangue, ou partie périphérique externe, ayant une épaisseur d'environ 5 nm, qui entoure les nanoparticules de Ti02. As can be seen in FIG. 2, there is indeed a shell, or gangue, or external peripheral portion, having a thickness of approximately 5 nm, which surrounds the TiO 2 nanoparticles.
La présence du bore turbostratique en périphérie des nanoparticules de Ti02 a été confirmée à l'aide de la spectroscopie Raman, The presence of turbostratic boron at the periphery of the TiO 2 nanoparticles was confirmed using Raman spectroscopy,
La figure 3 montre le spectre Raman des nanoparticules de Ti<な utilisées à l'exemple 1.  FIG. 3 shows the Raman spectrum of the Ti <な nanoparticles used in Example 1.
Ce spectre Raman présente trois pics à 395 cm-1, 516 cm-1 et 637 cm-1. This Raman spectrum has three peaks at 395 cm -1 , 516 cm -1 and 637 cm -1 .
La figure 4 montre le spectre Raman de l'échantillon de t-BN synthétisé à l'exemple comparatif 1. Ce spectre Raman présente un pic à 881 cm'1. Figure 4 shows the Raman spectrum of the t-BN sample synthesized in Comparative Example 1. This Raman spectrum has a peak at 881 cm -1 .
La figure 5 montre le spectre Raman des nanoparticules composites synthétisées à l'exemple 1.  Figure 5 shows the Raman spectrum of the composite nanoparticles synthesized in Example 1.
Comme on le voit en figure 5, les pics à 395 cm-', 516 cm-1 et 637 cm-1, représentatifs de Ti(½ sont présents ainsi que le pic à 881 cm-1 représentatif du nitrure de bore turbostratique. As can be seen in FIG. 5, the peaks at 395 cm -1 , 516 cm -1 and 637 cm -1 representative of Ti (½ are present as well as the peak at 881 cm -1 representative of turbostratic boron nitride.
Ainsi, les nanoparticules composites à l'exemple 1 sont bien constituées des nanoparticules de Ti02 recouvertes du nitrure de bore turbostratique. Thus, the composite nanoparticles in Example 1 consist of TiO 2 nanoparticles coated with turbostratic boron nitride.
Exemple 2  Example 2
Cet exemple a pour but de montrer l'efficacité de l'étanchéité de la partie périphérique externe ou coquille ou gangue des nanoparticules composites fabriquées à l'exemple 1.  This example is intended to show the effectiveness of the sealing of the outer peripheral part or shell or gangue composite nanoparticles manufactured in Example 1.
Pour cela, les nanoparticules de l'exemple 1 ont été noyées dans une résine non polymérisée. La quantité de nanoparticules composites de l'exemple 1 était de 1% en masse par rapport à la masse totale résine non polymérisée plus nanoparticules composites de l'exemple l . For this, the nanoparticles of Example 1 were embedded in a non-polymerized resin. The amount of composite nanoparticles of Example 1 was 1% by weight relative to the total mass of unpolymerized resin plus composite nanoparticles of Example 1.
Puis la résine a été polymérisée.  Then the resin was polymerized.
Dans le cas de l'exemple 2, la résine était une résine époxy.  In the case of Example 2, the resin was an epoxy resin.
Cependant, d'autres résines telles que les polyuréthanes ou les polyimides peuvent également être utilisées.  However, other resins such as polyurethanes or polyimides can also be used.
Exemple comparatif 2  Comparative Example 2
Un échantillon a été fabriqué avec la même résine que celle qui a été utilisée à l' exemple 2.  A sample was made with the same resin as used in Example 2.
L'efficacité de Pétanchéité de la partie externe en nitrure de bore turbostratique a été vérifiée par des tests de claquage effectués sur l'échantillon obtenu à l'exemple 2 et sur l'échantillon obtenu à l'exemple comparatif 2, The sealing efficiency of the turbostratic boron nitride outer part was verified by breakdown tests carried out on the sample obtained in Example 2 and on the sample obtained in Comparative Example 2,
En effet, le Ti02 ne peut pas être utilisé en tant que charge pour des applications dans des résines pour augmenter la conductivité thermique de ces résines sans affecter les propriétés de claquage : sous champs les ions de la surface des particules de Ti02 (Ti4 + ou Ti3 +) voire même les radicaux oxygène se déplacent et finissent par faire claquer l'échantillon. Indeed, the Ti0 2 can not be used as a filler for applications in resins to increase the thermal conductivity of these resins without affecting the breakdown properties: in the field the ions of the surface of TiO 2 particles (Ti 4 + or Ti 3 + ) or even the oxygen radicals move and eventually snap the sample.
La figure 7 représente les résultats du test de claquage de l'échantillon obtenu à l'exemple comparatif 2 : la tension de claquage est de 20 kV/mm.  FIG. 7 represents the results of the breakdown test of the sample obtained in Comparative Example 2: the breakdown voltage is 20 kV / mm.
La figure 8 représente les résultats du test de claquage effectué sur l'échantillon obtenu à l'exemple 2. Cette figure montre que dans ce cas, la tension de claquage est de 35 kV/mm.  FIG. 8 represents the results of the breakdown test performed on the sample obtained in example 2. This figure shows that in this case, the breakdown voltage is 35 kV / mm.
Ces tests de claquage montrent que la couche de nitrure de bore turbostratique n'est pas poreuse car, dans le cas contraire, il y aurait une tension de claquage bien plus faible dans le cas de l'échantillon de l'exemple 2,  These breakdown tests show that the turbostratic boron nitride layer is not porous because, otherwise, there would be a much lower breakdown voltage in the case of the sample of Example 2,
Exemple comparatif 3  Comparative Example 3
Les nanoparticules de Ti02 utilisées à l'exemple 1 ont été dispersées dans la même résine époxy qu'à l'exemple 2 et qu'à l'exemple comparatif 2. Cependant, la plaque obtenue n'était pas homogène et aucun de test de diffusivité et de claquage n'a été effectué car le résultat obtenu aurait été différent suivant la plaque choisie pour effectuer une mesure. Ceci montre qu'il n'y a pas compatibilité entre les nanoparticules de Ti02 et les résines organiques. The TiO 2 nanoparticles used in Example 1 were dispersed in the same epoxy resin as in Example 2 and in Comparative Example 2. However, the plate obtained was not homogeneous and no diffusivity and breakdown test was carried out because the result obtained would have been different depending on the plate chosen to carry out a measurement. This shows that there is no compatibility between TiO 2 nanoparticles and organic resins.
Exemple comparatif 4  Comparative Example 4
Le nitrure de bore turbostratique obtenu à l'exemple comparatif î a été introduit dans la même résine époxy qu'utilisée à l'exemple 2 et à l'exemple comparatif 2.  The turbostratic boron nitride obtained in Comparative Example 1 was introduced into the same epoxy resin as used in Example 2 and Comparative Example 2.
La quantité de nitrure de bore turbostratique était de 1% en masse, par rapport à la masse totale de résine non polymérisée plus le nitrure de bore turbostratique.  The amount of turbostratic boron nitride was 1% by weight, based on the total mass of unpolymerized resin plus turbostratic boron nitride.
La figure 6 montre les valeurs de diffusivité thermique à 23 °C des échantillons obtenus à l'exemple comparatif 2, à l'exemple comparatif 3 et à l'exemple 2.  FIG. 6 shows the thermal diffusivity values at 23 ° C. of the samples obtained in Comparative Example 2, Comparative Example 3 and Example 2.
Comme on le voit en figure 6, la conductivité thermique de l'échantillon obtenu à l'exemple 2, contenant les nanoparticules composites de l'invention, est augmentée de 16% par rapport à la conductivité thermique de l'échantillon obtenu à l'exemple comparatif 2, constitué uniquement de résine époxy et par rapport à l'échantillon obtenu à l'exemple 3 ne contenant que le nitrure de bore turbostratique.  As can be seen in FIG. 6, the thermal conductivity of the sample obtained in example 2, containing the composite nanoparticles of the invention, is increased by 16% relative to the thermal conductivity of the sample obtained in FIG. Comparative Example 2, consisting solely of epoxy resin and with respect to the sample obtained in Example 3 containing only turbostratic boron nitride.
Ainsi, les nanoparticules composites de l'invention peuvent être utilisées en tant que charge pour augmenter la conductivité thermique de résines ou de fluides aromatiques tels que les huiles à base de terphényle.  Thus, the composite nanoparticles of the invention can be used as a filler to increase the thermal conductivity of resins or aromatic fluids such as terphenyl-based oils.

Claims

REVENDICATIONS
1. Nanoparticule composite en un matériau choisi parmi Ti02, Zr02, ZnO, SiO2, AI2O3, Pt, Au, Ag, Cu, et une partie externe périphérique en nitrure de bore turbostratique (t-BN). 1. Composite nanoparticle of a material selected from Ti0 2 , Zr0 2 , ZnO, SiO 2 , Al 2 O 3 , Pt, Au, Ag, Cu, and a peripheral outer portion of turbostratic boron nitride (t-BN).
2. Nanoparticule selon la revendication 1 , caractérisée en ce que ladite partie interne centrale a des dimensions comprises entre 10 et 100 nm et une forme globalement sphéroïdale, en ledit matériau, et en ce que ladite partie externe en nitrure de bore turbostratique couvre entièrement la nanoparticule avec une épaisseur comprise entre 1 et 10 nm, de préférence une épaisseur de 5 nm.  2. A nanoparticle according to claim 1, characterized in that said central internal portion has dimensions of between 10 and 100 nm and a globally spheroidal shape, said material, and in that said outer portion turbostratic boron nitride completely covers the nanoparticle with a thickness of between 1 and 10 nm, preferably a thickness of 5 nm.
3. Nanoparticule selon la revendication 1 ou 2, caractérisée en ce que ladite partie interne centrale est en Ti02 ou en AI2O3. 3. Nanoparticle according to claim 1 or 2, characterized in that said central inner portion is Ti0 2 or AI2O3.
4. Nanoparticule selon l'une quelconque des revendications 1 à 3, caractérisée en ce que ladite partie interne centrale est en Ti02. 4. Nanoparticle according to any one of claims 1 to 3, characterized in that said central internal portion is Ti0 2 .
5. Utilisation des nanoparticules composites selon l'une quelconque des revendications 1 à 4 en tant que charge pour augmenter la conductivité thermique des matériaux dans lesquels elle est intégrée.  5. Use of the composite nanoparticles according to any one of claims 1 to 4 as a filler for increasing the thermal conductivity of the materials in which it is integrated.
6. Utilisation selon la revendication 5, caractérisée en ce que le matériau dans lequel les nanoparticules composites sont intégrées est une résine choisie parmi une résine époxy, une résine polyuréthane et une résine polyimide, de préférence est une résine époxy.  6. Use according to claim 5, characterized in that the material in which the composite nanoparticles are integrated is a resin chosen from an epoxy resin, a polyurethane resin and a polyimide resin, preferably an epoxy resin.
7. Utilisation selon la revendication 6, caractérisée en ce que les nanoparticules composites représentent entre 0,1 et 5 % massique, par rapport au poids total de la résine non réticulée plus les nanoparticules composites.  7. Use according to claim 6, characterized in that the composite nanoparticles represent between 0.1 and 5% by weight, relative to the total weight of the non-crosslinked resin plus the composite nanoparticles.
8. Matériau composite comprenant une résine dans laquelle des nanoparticules composites selon l'une quelconque des revendications 1 à 4 sont noyées.  8. Composite material comprising a resin in which composite nanoparticles according to any one of claims 1 to 4 are embedded.
9. Matériau composite selon la revendication 8, caractérisé en ce que la résine est choisie parmi une résine époxy, une résine polyuréthane, et une résine polyimde, de préférence est une résine époxy.  9. Composite material according to claim 8, characterized in that the resin is selected from an epoxy resin, a polyurethane resin, and a polyimide resin, preferably an epoxy resin.
10. Utilisation des nanoparticules selon la revendication 3 en tant qu'agent de protection contre les rayons UV. 10. Use of the nanoparticles according to claim 3 as an agent for protection against UV rays.
1 1. Utilisation des nanoparticuîes selon la revendication 4 en tant qu'agent opacifiant pour des fibres papetières. 1. Use of the nanoparticles according to claim 4 as an opacifying agent for paper fibers.
12. Procédé de synthèse de nanoparticuîes composites selon l'une quelconque des revendications 1 à 4, caractérisé en ce qu'il comprend les étapes suivantes :  12. Process for synthesizing composite nanoparticles according to any one of claims 1 to 4, characterized in that it comprises the following steps:
a) dispersion de nanoparticuîes en un matériau choisi parmi Ti02; Zr02, ZnO, Si02, AI2O3, Pt, Au, Ag, Cu, dans de l'éthanol dans lequel de l'acide borique et de l'urée ont été dissous, par traitement aux ultrasons pendant entre 15 minutes et 4 heures, après ajout d'eau. a) dispersion of nanoparticles in a material selected from Ti0 2; Zr0 2 , ZnO, SiO 2 , Al 2 O 3, Pt, Au, Ag, Cu, in ethanol in which boric acid and urea were dissolved, by sonication for between 15 minutes and 4 hours , after adding water.
b) évaporation de l'éthanol,  b) evaporation of the ethanol,
c) séchage du solide obtenu après l'étape b) pendant entre 24 et 120 heures, de préférence 96 heures, à une température comprise entre 60 et 100°C, de préférence à 80°C, et  c) drying the solid obtained after step b) for between 24 and 120 hours, preferably 96 hours, at a temperature between 60 and 100 ° C, preferably at 80 ° C, and
d) traitement thermique du solide obtenu à l'étape c) à une température comprise entre 400°C et 500°C, de préférence à 500°C, pendant entre 1 et 5 heures, de préférence 3 heures.  d) heat treatment of the solid obtained in step c) at a temperature between 400 ° C and 500 ° C, preferably at 500 ° C, for between 1 and 5 hours, preferably 3 hours.
13. Procédé selon la revendication 12, caractérisé en ce que, à l'étape a), la quantité d'urée correspond à deux fois la quantité stœchiométrique de bore apporté par l'acide borique.  13. The method of claim 12, characterized in that, in step a), the amount of urea is twice the stoichiometric amount of boron provided by boric acid.
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